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authorDaniel De Graaf <dgdegra@tycho.nsa.gov>2011-10-28 01:58:47 +0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-11-22 02:14:48 +0400
commit420eb554d5ee6daad743d8190383219f757dd66c (patch)
tree0c8b69dbc2de5aea96be93a24a8b39dbb9256b88 /drivers/xen/events.c
parent0cc678f850f2cba0cedbd133fcbbf175554cd6c6 (diff)
downloadlinux-420eb554d5ee6daad743d8190383219f757dd66c.tar.xz
xen/event: Add reference counting to event channels
Event channels exposed to userspace by the evtchn module may be used by other modules in an asynchronous manner, which requires that reference counting be used to prevent the event channel from being closed before the signals are delivered. The reference count on new event channels defaults to -1 which indicates the event channel is not referenced outside the kernel; evtchn_get fails if called on such an event channel. The event channels made visible to userspace by evtchn have a normal reference count. Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen/events.c')
-rw-r--r--drivers/xen/events.c74
1 files changed, 73 insertions, 1 deletions
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 6e075cdd0c6b..a3bcd6175f4a 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -87,6 +87,7 @@ enum xen_irq_type {
*/
struct irq_info {
struct list_head list;
+ int refcnt;
enum xen_irq_type type; /* type */
unsigned irq;
unsigned short evtchn; /* event channel */
@@ -406,6 +407,7 @@ static void xen_irq_init(unsigned irq)
panic("Unable to allocate metadata for IRQ%d\n", irq);
info->type = IRQT_UNBOUND;
+ info->refcnt = -1;
irq_set_handler_data(irq, info);
@@ -469,6 +471,8 @@ static void xen_free_irq(unsigned irq)
irq_set_handler_data(irq, NULL);
+ WARN_ON(info->refcnt > 0);
+
kfree(info);
/* Legacy IRQ descriptors are managed by the arch. */
@@ -637,7 +641,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
if (irq != -1) {
printk(KERN_INFO "xen_map_pirq_gsi: returning irq %d for gsi %u\n",
irq, gsi);
- goto out; /* XXX need refcount? */
+ goto out;
}
irq = xen_allocate_irq_gsi(gsi);
@@ -939,9 +943,16 @@ static void unbind_from_irq(unsigned int irq)
{
struct evtchn_close close;
int evtchn = evtchn_from_irq(irq);
+ struct irq_info *info = irq_get_handler_data(irq);
mutex_lock(&irq_mapping_update_lock);
+ if (info->refcnt > 0) {
+ info->refcnt--;
+ if (info->refcnt != 0)
+ goto done;
+ }
+
if (VALID_EVTCHN(evtchn)) {
close.port = evtchn;
if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
@@ -970,6 +981,7 @@ static void unbind_from_irq(unsigned int irq)
xen_free_irq(irq);
+ done:
mutex_unlock(&irq_mapping_update_lock);
}
@@ -1065,6 +1077,66 @@ void unbind_from_irqhandler(unsigned int irq, void *dev_id)
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
+int evtchn_make_refcounted(unsigned int evtchn)
+{
+ int irq = evtchn_to_irq[evtchn];
+ struct irq_info *info;
+
+ if (irq == -1)
+ return -ENOENT;
+
+ info = irq_get_handler_data(irq);
+
+ if (!info)
+ return -ENOENT;
+
+ WARN_ON(info->refcnt != -1);
+
+ info->refcnt = 1;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(evtchn_make_refcounted);
+
+int evtchn_get(unsigned int evtchn)
+{
+ int irq;
+ struct irq_info *info;
+ int err = -ENOENT;
+
+ mutex_lock(&irq_mapping_update_lock);
+
+ irq = evtchn_to_irq[evtchn];
+ if (irq == -1)
+ goto done;
+
+ info = irq_get_handler_data(irq);
+
+ if (!info)
+ goto done;
+
+ err = -EINVAL;
+ if (info->refcnt <= 0)
+ goto done;
+
+ info->refcnt++;
+ err = 0;
+ done:
+ mutex_unlock(&irq_mapping_update_lock);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(evtchn_get);
+
+void evtchn_put(unsigned int evtchn)
+{
+ int irq = evtchn_to_irq[evtchn];
+ if (WARN_ON(irq == -1))
+ return;
+ unbind_from_irq(irq);
+}
+EXPORT_SYMBOL_GPL(evtchn_put);
+
void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
int irq = per_cpu(ipi_to_irq, cpu)[vector];